Conventionally, frequency allocation for a new service or frequency allocation to a new provider was performed under the leading of the government.
Particularly, when new providers were added to existing providers, frequencies as limited resources were allocated by allocating new frequencies to the new providers through an auction, etc., or by collecting existing frequencies from the existing providers and reallocating the collected frequencies to the new providers.
However, as demands radio data traffic are explosively increased due to the spread of various wireless Internet-based applications such as an open terminal platform, an application (app) store and a mobile VoIP in recent years, the frequency allocation under the leading of the government is very inefficient, and it gradually becomes difficult to secure new frequencies on Frequency Allocation Table.
Particularly, with the rapid development of broadcasting and communication systems, next-generation communication systems are designed in the form of fusion of several networks, and the necessity of interaction gradually increases as the systems are gradually complicated. In addition, the use of frequency resources increases as communication technologies and services are developed, and the problem of the lack of frequencies is serious as specific frequency bands are occupied to provide excellent communication technologies and services.
Recently, attention to a frequency sharing technology has been paid as a plan for solving the problem. The current lack of frequencies results from the existing frequency management technology in which frequencies are partitioned. However, the frequency sharing technology is derived from the viewpoint that although it seems that frequencies are insufficient on the Frequency Allocation Table, the problem of lack of frequencies can be solved through the frequency sharing technology.
As the problem of the lack of frequencies are recognized as an important issue all over the world, the US Federal Communications Commission (FCC) decided to apply a cognitive radio (CR) technology as the frequency sharing technology to TV idle frequencies (whitespaces) so as to improve spectrum use efficiency and to facilitate the introduction of new services, and revised related regulations in November, 2008.
Such a movement is gradually extended, and, in 2009, England permitted the used of a CR-based frequency sharing technology in frequency bands not spatially used, i.e., whitespace bands, among TV broadcasting frequency bands. Currently, EU is also under investigation on a plan for introducing the CR-based frequency sharing technology in the whitespace bands, and preparations for providing a frequency sharing policy using whitespace bands is made in Korea.
The cognitive radio technology refers to a system that allows a communication device to detect communication environment for itself, to determine and select an operational method for optimum communication and to make a plan for future decision from the previous communication experiences. That is, the cognitive radio technology is a technology for searching for idle resources (spectrum holes or whitespaces) which have low utilization or are not temporarily/spatially used from frequency bands allocated in unlicensed bands and adaptively and opportunistically utilizing the searched idle resources. In this case, the cognitive radio technology should be operated not to damage a primary user by immediately stopping the use of a corresponding band or adjusting transmission power when the primary user having a license of the corresponding band is found.